The woylie, or brush-tailed bettong, is a small nocturnal marsupial that plays an important role in maintaining the health of its habitat. Formerly widespread across much of Australia, the woylie declined dramatically following European colonisation. However, extensive conservation efforts throughout the 1970s, 1980s and 1990s brought the species back from the brink of extinction; the woylie became the first mammal in Australia to be removed from threatened species lists as a result of conservation action. Unfortunately the species has once again suffered a population crash with populations estimated to have declined by more than 80% over the past decade. Researchers are racing against the clock to identify the cause of the declines so that appropriate conservation action can be taken.

Urgent Conservation Actions

Identify the cause of recent population declines so that appropriate conservation action can be taken.

The woylie is a macropodoid marsupial in the family Potoroidae (potoroos, bettongs or rat-kangaroos). These species are small marsupials which hop on their hindfeet, dig for much of their food with well-developed forefeet, and have a complex stomach that allows them to extract nutrition very efficiently from their diet. Fossil members of this family are known from the middle Miocene of Australia (16 million years ago).

The Potoroidae contains several small genera, including Bettongia (the bettongs, such as the burrowing bettong and the brush-tailed bettong) and Potorous, containing the potoroos.

There are two subspecies of woylie: Bettongia penicillata penicillata and B. p. ogilbyi. The latter is believed to be extinct.

Description

Size:

Head and body length: 300 – 380 mm

Weight: 1.1 - 1.6 kg

The woylie, or brush-tailed bettong, is a small marsupial with a distinctive crest of black fur that extends the length of its prehensile tail. The dense fur is yellowish-grey in colour above and paler underneath. The eyes are large, the ears are short and rounded and the tip of the muzzle is naked and flesh coloured. The hind feet are longer than the head. Females have four mammae and a well-developed pouch.

Ecology

Woylies are mostly solitary, occupying individual home ranges of around 20-40 ha, an unusually large area for animals of their size. Each home range includes a nesting area which is usually well-defended, and a feeding area which may overlap with those of neighbouring animals. Woylies are primarily nocturnal, spending the daylight hours in an elaborate domed nest made of grass or shredded bark, built over a shallow depression scraped in the ground, under a bush or other cover. They forage for food from dusk until an hour or two before dawn. Their diet consists primarily of the fruiting bodies of underground fungi, supplemented by bulbs, tubers, seeds, insects and resin, probably from Hakea shrubs. Bacteria in their stomachs break down the fungi and release digestible nutrients. The fungal spores are not digested but pass through the animals unharmed and are deposited in faeces in a new location, thus creating a mutually beneficial relationship. Fungi are also beneficial to trees as they assist with nutrient uptake from the soil, so in dispersing the fungi, the woylie plays an important role in maintaining the health of the forest. Woylies extract all the water they need from their diet so rarely need to drink.

Breeding takes place throughout the year with females producing a single young after a gestation period of 21 days. The young remains in the mother’s pouch for about 98 days. After leaving the pouch the young remains close to the mother, sharing the nest and even continuing to suckle, until the next infant vacates the pouch and displaces it. Females give birth to their first young at around 6 months of age and approximately every 100 days thereafter for the rest of their lives. They live for four to six years in the wild.

Habitat

The woylie formerly inhabited a variety of habitats, from temperate forests to desert spinifex grasslands. It is now restricted to forests, open woodlands and mallee shrublands with a dense, low understory of tussock grasses or woody scrub.

Distribution

Endemic to Australia, the woylie formerly ranged across much of the Australian mainland south of the tropics. Two subspecies are recognised: Bettongia penicillata penicillata, which occurred in south-eastern Australia, and is now considered extinct, and B. p. ogilbyi which currently occurs as natural populations at Dryandra Woodland, Upper Warren (Perup Nature Reserve and adjacent areas), and at Tutanning Nature Reserve in southwest Australia.

The species has also been translocated to several sites in Western Australia, South Australia and New South Wales.

Decreasing. Between 2001 and 2006 it is estimated that the species had declined by 70-80% (approximately 8,000-15,000 individuals). The declines have continued and there are no clear signs of population recovery.

Once abundant across much of Australia, this species has declined massively following European colonisation of Australia. Introduced exotic predators such as foxes and cats have played a role in the decline of this species, together with habitat loss and degradation resulting from changed fire regimes, conversion to agriculture and the effects of introduced herbivores such as rabbits and livestock. Disease may also have played a role in historical declines.

By the 1970s the species occurred at only three locations in the wild. However, recovery efforts and the commencement of broad-scale fox controls saw populations increase significantly over the next three decades. As a result the woylie was removed from State and Commonwealth threatened species lists.

The woylie population size reached a peak of approximately 40,000 individuals in 2001. However, unfortunately the species has once again suffered a population crash. Over the past decade populations are estimated to have declined by more than 80%. The cause of the declines, which have taken place in large populations at both original and reintroduction sites, are unclear but cat predation and disease (probably related to a low genetic diversity) have been implicated.

Conservation Underway

The woylie has been the subject of considerable research and conservation efforts. Following its listing in the Endangered Species Protection Act 1992 it was included in wildlife conservation programs such as the Australian Department of Environment and Conservation's (DEC) Western Shield. Successful conservation efforts in the 1980s and 90s concentrated on controlling the feral fox and reintroducing woylies from expanding populations to fox-free sites in its former range. It was successfully reestablished in many areas with substantial increases in population size, leading to it being the first animal to be removed from the threatened species list as a result of conservation actions, in 1996.

New populations have been established by translocation at Batalling Forest, Boyagin Nature Reserve, Julimar Forest, Lake Magenta Nature Reserve, Peron Peninsula at Shark Bay, and more recently, Kalbarri National Park. Woylies have also been translocated to a number of sites in the northern and southern Jarrah forests of Western Australia, and to sites in South Australia and New South Wales.

In both Western Australia and South Australia, reintroductions have occurred onto private property where a long term commitment to conservation efforts has been demonstrated. Woylies have been reintroduced to two private properties in Western Australia and three in South Australia. Woylies have also been translocated to fenced wildlife sanctuaries that are effectively managed as wild subpopulations (two in Western Australia, one in South Australia and one in NSW). These sanctuaries are owned and managed by the Australian Wildlife Conservancy.

Woylies have been recorded from seven nature reserves, 14 national parks, eight state forest areas, one timber reserve and two conservation parks. Populations occurring in state forest are not managed specifically for conservation, but are baited for foxes. Regular monitoring is carried out at 42 sites in Western Australia, 13 sites in South Australia and three in New South Wales. In 2007, the woylie was placed back on the WA list of priority species.

The Woylie Conservation Research Project was established in 2005 to investigate the causes of the recent population declines with a focus in the Upper Warren region. Lead by DEC, in collaboration with Murdoch University, Perth Zoo, the Australian Wildlife Conservancy and the University of Western Australia, the project is investigating the roles of predation, food resources, and disease. There is also a DEC research program focused on the predators and woylie populations at Dryandra and Tutanning.

Conservation Proposed

Existing research and conservation actions should continue. Ongoing fox control is important for the management of the species. There is a need to understand role of cats in population declines.